Tensionless–frictionless interaction of flexible annular foundation with a transversely isotropic multi‐layered half‐space          下载免费PDF全文

Morteza Eskandari‐Ghadi  Ghasem Gorji‐Bandpey  Azizollah Ardeshir‐Behrestaghi  Seyed Masoud Nabizadeh 《国际地质力学数值与分析法杂志》2015,39(2):155-174

A transversely isotropic multi‐layered half‐space, with axis of material symmetry perpendicular to the free surface, supports a flexible either annular or solid circle foundation. The contact area of the foundation and the half‐space is considered to be both frictionless and tensionless. The foundation is assumed to be affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems with different thickness of layers is the target of this paper. With the use of ring load Green's functions for both the foundation and the continuum half‐space, an integral equation accompanied with some inequalities is introduced to model the complex BVP. With the incorporation of ring‐shape FEM, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular and annular foundation with half‐space. Some new illustrations are presented to portray the aspect of the anisotropy and layering of the half‐space. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Numerical and theoretical research on stress distribution in the loosening zone of the trapdoor problem     

Luju Liang  Changjie Xu 《国际地质力学数值与分析法杂志》2019,43(7):1426-1447

The traditional theory of soil arching effect was developed on the assumption that stress distribution in the loosening zone is uniform. However, because of the deflection of principal stress' direction, the stress distribution in the loosening zone is actually ununiform. For the evaluation of principal stress axis deflection and stress redistribution, a discrete element method numerical model of trapdoor problem is established for the simulation of soil arching effect. Based on the numerical results, an arc shape of major principal stress trajectory and uniform horizontal stress distribution at the same depth of the loosening zone are adopted. An analytical model is raised to estimate the average loosening earth pressure acting on the trapdoor and stress distribution in the loosening zone at a limit state. In addition, comparison studies are carried out between the predictions of the proposed solutions and discrete element method numerical results as well as available model test results, thereby validating the accuracy of the proposed theoretical model. Both numerical and theoretical results indicate that the vertical stress distribution in the loosening zone is obviously ununiform. The load acting in the middle of loosening zone is transferred toward two sides so that the vertical stress distribution in loosening zone is concave.  相似文献   

How preferential flow delivers pre‐event groundwater rapidly to streams     

Stephen R.H. Worthington 《水文研究》2019,33(17):2373-2380

Groundwater often accounts for a substantial fraction of flood hydrographs, but the processes responsible for this have been unclear. However, many aquifers have preferential flow and this explains how aquifers can be so responsive. In bedrock aquifers, weathering enhances the connectivity and apertures along the most efficient flow paths and hence enhances the permeability. This results in celerities and velocities of the preferential flow in these dual‐porosity aquifers that are two to three orders of magnitude higher than if the aquifers behaved as single‐porosity media. The celerities have been determined from artificial and natural flood pulses, from tidal lags, and from pumping tests. Preferential‐flow velocities have been calculated from tests using applied tracers. Celerities in bedrock aquifers are typically one to two orders of magnitude faster than velocities. The ubiquitous preferential flow in aquifers provides an additional explanation, besides groundwater ridging, for the rapid release of groundwater to streams during storm events.  相似文献   

基于部分最小二乘岭估计的粗差定值定位     

金丽宏  吕玉婷  汪耀  许运鹏  张小龙 《测绘工程》2016,25(6):61-64

在利用部分最小二乘原理进行粗差定值定位时,模型的法方程矩阵可能存在病态性,使得到的粗差定值定位结果不可靠。文中针对观测数据包含多个粗差且法方程病态问题,利用岭估计处理病态问题,建立部分最小二乘岭估计的粗差定值定位方法,给出粗差搜索步骤,利用迭代算法实现多个粗差的定值和定位。通过模拟算例分析部分最小二乘法、部分最小二乘岭估计在粗差搜索方面的效果,从另一个角度探讨粗差处理方法,推广现有的误差理论,证明文中方法的有效性。  相似文献   

重力场数学拟合模型解的影响因素探究     

鹿荻  陈锴 《测绘科学》2016,41(3):28-33

为了提高地球重力场模型不适定方程求解的精度,该文采用谱分析方法从级数展开阶数、数据采样率及数据缺失量3个方面探索影响数学拟合效果的根本因素:从常用的三角级数及勒让德级数模型出发,引出重力场拟合模型球谐函数模型,观察在改变级数展开阶数、数据采样率及数据缺失量等情况下所对应设计矩阵谱结构的变化,并从微观上研究影响误差分配的有关因素及最小奇异值对误差的决定性作用,为探求重力场模型解不准的原因及实现更高精度的全球重力场模型的建立提供参考。  相似文献   

Dual Control of Depositional Facies on Uranium Mineralization in Coal‐bearing Series: Examples from the Tuanyushan Area of the Northern Qaidam Basin,NW China     

GUO Biao  SHAO Longyi  WEN Huaijun  HUANG Guangnan  ZOU Mingjun  LI Yonghong 《《地质学报》英文版》2018,92(2):733-754

The uranium deposits in the Tuanyushan area of northern Qaidam Basin commonly occur in coal-bearing series. To decipher the U-enrichment mechanism and controlling factors in this area, a database of 72 drill cores, including 56 well-logs and 3 sampling wells, was examined for sedimentology and geochemistry in relation to uranium concentrations. The results show that coal-bearing series can influence uranium mineralization from two aspects, i.e., spatial distribution and dynamic control. Five types of uranium-bearing rocks are recognized, mainly occurring in the braided river and braided delta sedimentary facies, among which sandstones near the coals are the most important. The lithological associations of sandstone-type uranium deposits can be classified into three subtypes, termed as U-coal type, coal-U-coal type, and coal-U type, respectively. The coal and fine siliciclastic rocks in the coalbearing series confined the U-rich fluid flow and uranium accumulation in the sandstone near them. Thus, the coal-bearing series can provide good accommodations for uranium mineralization. Coals and organic matters in the coal-bearing series may have served as reducing agents and absorbing barriers. Methane is deemed to be the main acidolysis hydrocarbon in the U-bearing beds, which shows a positive correlation with U-content in the sandstones in the coal-bearing series. Additionally, the δ13 C in the carbonate cements of the U-bearing sandstones indicates that the organic matters, associated with the coal around the sandstones, were involved in the carbonation, one important component of alteration in the Tuanyushan area. Recognition of the dual control of coal-bearing series on the uranium mineralization is significant for the development of coal circular economy, environmental protection during coal utilization and the security of national rare metal resources.  相似文献   

基于无机成因的油气勘查概念模型(BRCF)     

舒思齐  张洪涛  肖序常 《地质通报》2018,37(5):920-929

基于超基性岩蛇纹石化成油理论,根据构造条件和沉积条件,提出了石油勘查概念模型——"BRCF"模型:B代表侵入地壳超基性岩;R代表储油层;C代表盖层;F代表深大断裂。运用该模型分析了波斯湾地区油气田和中国典型油气田油气成藏规律,并预测了中国大陆油气勘查靶区。  相似文献   

黄河流域地下水资源状况及其生态环境问题   总被引：1，自引：0，他引：1       下载免费PDF全文

韩双宝  李甫成  王赛  李海学  袁磊  刘景涛  申豪勇  张学庆  李长青  吴玺  马涛  魏世博  赵敏敏 《中国地质》2021,48(4):1001-1019

黄河流域是中国重要的生态屏障和经济地带,上中下游面临着不同生态环境问题,水在生态环境问题的形成演化过程中起着重要作用。本文从黄河流域地下水动态特征、地下水资源的数量、质量及开发利用等方面,分析了黄河流域地下水资源及饮水安全状况。黄河流域年度地下水资源量393.55亿m~3,银川平原、河套平原等7处主要平原(盆地)地下水资源量为81.91亿m~3,占比超过20%;黄河流域地下水质量以Ⅰ～Ⅳ类为主,劣质地下水主要受总硬度、硫酸盐、铁、溶解性总固体等天然原生组分影响,砷、氟、硒、碘等原生组分超标是流域部分地区地下水饮水安全的主要威胁;2020年与2019年同期相比,黄河流域地下水位呈上游稳定、中游局部上升、下游下降的态势,主要地下水降落漏斗形态基本稳定。针对黄河源区、宁蒙河套平原等重点区段,分析了存在的主要生态环境问题,提出了全面开展流域水文地质与水资源调查评价,深入开展黄河流域及重点地区水平衡分析等工作建议。  相似文献   

页岩气水平井TOC测井评价新方法     

刘伟男  张超谟  朱林奇  胡松  孔政  邓瑞 《物探与化探》2021,(2):423-431

由于存在地层缺失、井眼穿层不断变化、重点层段测井曲线较少、井眼环境复杂、测井响应值与储层参数关系较为复杂等特点,页岩气储层水平井测井解释难度较大。针对该问题,本文采用“水平井钻遇地层模型—水平井间及水平井与直井响应差异分析—水平井曲线校正—基于直井的参数评价模型”的评价技术流程,进行页岩气水平井TOC测井评价。在测井评价中,针对响应规律复杂的特点,采用直方图法进行测井响应规律分析,同时考虑到水平井测井曲线较少,为了综合利用测井曲线信息,结合曲线重叠方法提出双重信息融合评价模型。结果表明,本方法在充分分析测井响应差异的基础上对水平井测井曲线进行校正,且提出的双重信息融合模型具有能充分利用测井信息、评价精度高以及操作简单等优点。  相似文献   

基于标准差分析法的X波段双偏振天气雷达资料质量评估     

李思腾  仰美霖  李林  张舒婷  张治国  潘昱冰 《干旱气象》2019,37(3):467-476

2015年9月,北京市气象局在北京地区架设4部X波段双线偏振天气雷达并开展了观测试验。本文利用其中3部雷达在2016年6月30日的观测数据,用标准差分布统计方法,对雷达的观测参量进行初步质量评估。结果表明:(1)3部雷达反射率标准差符合理论值的数据占总观测数据的73.5%~77.9%,反射率的数据波动基本符合理论分布;(2)3部雷达差分反射率标准差符合理论值的数据占总观测数据的68.4%~81.4%,其中房山雷达数据波动较大;(3)3部雷达互相关系数标准差符合理论值的数据占总观测数据的45.7%~63.5%,其中房山雷达数据波动最大,其他2部雷达都有同程度的数据波动;(4)3部雷达差分传播相位标准差符合理论值的数据占总观测数据的73.5%~83.9%,其中房山雷达数据波动相对较大,与雷达其他观测参量相比,差分传播相位的波动较小。  相似文献